This invention relates to polymeric implements that transmit torque.
Torque transmission is important in many areas. For example, in the field of less invasive surgery, catheters and guidewires are threaded along tortuous paths to treatment sites deep within the body by torquing and pushing their proximal end. Positioning these devices is easier if they have torque transmission characteristics such that when the physician rotates the proximal end, the distal end rotates by a corresponding amount. Accurate torque transmission is also important for medical devices with rotating parts, such as an acoustic imaging catheter with a transducer that is rotated by a driveshaft.
In an aspect, the invention features an elongated medical instrument formed at least in part by an extended element that is subject to torque in use. The element is a structural body composed of polymer that is helically oriented about the instrument axis.
In another aspect, the invention features an elongated medical instrument formed at least in part of an extended element that is a structural body composed of polymer. The element has a length between about 40 to 300 inch and an outer diameter of about 0.25 inch or less. The element is capable of substantially 1:1 torque transmission between the proximal and distal ends without substantial whipping when the member is looped in a circle with a diameter about 5 inch at a point about half way along its length.
In another aspect, the invention features an elongated medical instrument formed at least in part of an extended element and a method for forming the element. The element is a structural body that is composed of polymer and which is the product of the process of providing an elongated polymer member, heating the polymer member above its glass transition temperature but below its melting temperature, simultaneously twisting and tensioning member, and cooling the member to set the effect of the twisting and tensioning into the member.
Embodiments may include one or more of the following. The element may have a length of about 40 inch or more and a diameter of about 0.25 to 0.008 inch. The helical paths may have a pitch length that is about 1.5 or more times the outer diameter of the element. The helical paths may have a pitch length from about 2 to about 5 times the outer diameter of the element.
Embodiments may also include one or more of the following. The medical instrument may be composed entirely of polymer. The polymer may be a semi-crystalline polymer. The polymer may be PET, Nylon, or PEBAX. The polymer may be oriented or heat set at a temperature substantially greater than sterilization temperature.
Embodiments may also include one or more of the following. The element may be in the form of a solid polymer rod. The element may be in the form of a tube. The medical instrument may be in the form of a composite of an elongated metal member and the polymeric element. The element may be a coextrusion of polymers. The element may be a coextrusion of different polymers. The instrument may have differential stiffness along its axis. The element may include polymer molecules oriented on helical paths and polymer molecules oriented linearly, along the axis. The element may include polymer molecules oriented on helical paths oriented about the axis in opposite directions. The element may include a first polymer layer with polymer molecules oriented along helical paths extending in one direction about the axis and a second polymer layer with polymer molecules oriented along helical paths extending in the opposite direction about the axis. The medical instrument may be in the form of a medical guidewire. The medical instrument may be in the form of a medical catheter having a lumen therethrough. The medical instrument of may be stiffer in a proximal portion than a distal portion.
Embodiments may also include one or more of the following. The process may include stretching the member by the tensioning. The process may include placing the polymer member in tension and rotating one end of the polymer member while holding the other end rotationally stationary. The process may include simultaneously heating, twisting, and stretching. The process may include providing a member having differential stiffness along its length. The process may include heating to improve dimensional stability. The process may include forming a tube by providing an elongated polymer member constructed of a jacket and core composed of different polymers, heating, twisting, tensioning, and cooling the member, heating to a temperature sufficient to melt or relax the core polymer without melting or relaxing the core polymer, and removing the core polymer to form a lumen.
In another aspect, the invention features an apparatus for manufacturing an elongated element that is subject to torque in use and composed of polymer. The apparatus includes first and second holding stations spaced along a linear path and constructed to grip a preformed polymer member. Translating apparatus is provided for moving the first and second stations along the path to place the preformed polymer member in tension. Torquing device is provided for imposing torque on the preformed member, and a heater is located between the first and second stations for heating a portion of the preformed member.
Embodiments may include one or more of the following. The torquing device may be a rotatable chuck provided at the first holding station. The translating apparatus may be constructed to move the stations along the linear path in the same direction. The translating apparatus may be constructed to move the second station faster than the first station to stretch the member therebetween. The second holding station may include a series of grippers to hold and support a processed length of the member while other portions are processed. The heater may heat the member without contacting the member. The heater may be a heat gun. The translating apparatus may be constructed to vary the translation speed of the stations during the course of a processing. The torquing device may be constructed to vary the torque during the course of processing the member. The translating apparatus, torque device, and heater may be constructed to reverse the direction of movement along the path while keeping the member in tension and without torquing, to heat the member to improve dimensional stability. The holding stations and torque device may be constructed to contact the member on its exterior surface. The holding stations and torque device may be constructed to contact a preformed polymer tubular member with a core member extending therethrough in a manner to permit torquing and tensioning the polymer member without torquing or tensioning the core member, while translating the tubular member and core member along the path. The torquing element may be a rotatable chuck positioned at the first station permitting gripping and torquing the polymer member without gripping or torquing the core and the second station includes a gripping element that grips the polymer member and the core together.
In another aspect, the invention features an elongated medical instrument that is delivered into tortuous pathways deep within the body. The instrument has an extended element having differential stiffness along its length, composed of homogenous structural polymer that is helically oriented about the instrument axis.
Embodiments may also include one or more of the following. The element may include polymers of differing stiffness along its length. The element may include variable diameter along its length. The element may be stiffer in proximal portions than distal positions. The instrument may be a tube-form catheter. The instrument may be a solid rod-form. The instrument may be a guidewire.
In another aspect, the invention features an elongated implement that is torqued in use. The implement has an extended element having a first portion composed of a polymer that is helically oriented about the instrument axis and a second portion composed of polymer in a different orientation.
Embodiments may also include one or more of the following. The second portion may be composed of polymer that is helically oriented in the rotational direction opposite the helical orientation of the first portion. The second portion may be composed of polymer that is linearly oriented. The first and second portions may be separate layers. The first and second portions may be disposed along the length of the device. The implement may be in the form of a tube. The implement may be in the form of a solid rod-form. The implement may be in the form of a rotatable drive shaft.
In another aspect, the invention features an elongated implement that is subject to torque in use. The implement includes an extended jacket element composed of polymer that is helically oriented about the implement axis and positioned over a core element.
Embodiments may also include one or more of the following. The core element may be a metal wire. The wire may be a superelastic material. The core may be a glass filament.
In another aspect, the invention features an elongate implement that is subject to torque in use. The implement has a first portion made of an extended jacket element of polymer positioned over a core element, and a second portion composed substantially of a polymer.
Embodiments may include one or more of the following. The core element extends partially into the second portion. The first portion has substantially greater length than the second portion. The second portion is substantially of a polymer that is helically oriented about the instrument axis.
In another aspect the invention features a medical procedure on a body. The procedure includes providing an elongated medical instrument formed at least in part by an extended element that is subject to torque in use. The element is a structural body of polymer that is helically oriented about the instrument axis. The procedure also includes delivering the medical instrument into the body and applying torque to the part comprised of polymer that is helically oriented about the instrument.
Embodiments may also include one or more of the following. The procedure includes providing the medical instrument in the form of a guidewire and delivering the instrument into a body lumen by urging and torquing an end of the instrument. The procedure includes applying electrical or magnetic energy in proximity to the medical instrument. The procedure is a sphincterotomy procedure and the part made of polymer is made entirely of polymer near the distal end of the guidewire. The procedure includes delivering the guidewire into a body lumen, guiding a sphinctertome into the lumen over the guidewire, the sphinctertome including an electrically-energized resecting element near its distal end adapted to resect tissue, and resecting tissue with the resecting element while maintaining the guidewire in axial location corresponding to the resecting element.
Embodiments also include one or more of the following. The medical procedure is performed while simultaneously conducting magnetic resonance imaging of the body. The procedure is a less invasive procedure. The procedure includes delivering a guidewire into the body. The procedure includes delivering a catheter into the body. The procedure includes delivering the medical instrument into the body through an entry needle formed of metal.
Embodiments may also include one or more of the following advantages. For example, whipping can be decreased or eliminated in guidewires, catheters, and other devices. Whipping can occur if torque is not efficiently transmitted, causing a device to become twisted and wound along its length. If the distal end of the member does not respond to the rotational torque applied at the proximal end in a one-to-one relationship, then the torsional energy is stored in the length of the member and the distal tip will whip when a threshold energy is reached.
In embodiments, rotational fidelity between the proximal and distal ends may be substantially 1:1, even for devices of extended length, e.g., 20 inch or more, e.g. 75 inch, that follow a tortuous path, e.g., a tight circle.
Moreover, by providing high torque fidelity components according to the invention, the use of common polymers in medical devices can be extended. Accordingly, the invention can reduce instrument weight, improve device lubricity, simplify manufacture, and lower cost.
Further features, aspects, and advantages follow. For example, in some further aspects, the invention features methods of medical treatment using polymeric torque transmission elements and apparatus for forming polymeric torque transmitting elements, as well as non-medical devices and methods employing torque transmission.